C-reactive protein (also known as CRP and PTX1) is an essential human acute-phase reactant produced in the liver in response to a variety of inflammatory cytokines. The protein, first identified in 1930, is highly conserved and considered to be an early indicator of infectious or inflammatory conditions. Plasma CRP levels increase 1,000-fold in response to infection, ischemia, trauma, burns, and inflammatory conditions. Since the biological half-life of CRP is not influenced by age, liver or kidney function or pharmacotherapy, it is reliable biochemical marker for tissue destruction, necrosis and inflammation and its measurement is widely used to monitor various inflammatory states, angina pectoris, vascular insults, end-stage renal disease, rheumatoid arthritis, obesity and atherosclerosis (Arici and Walls, Kidney Int., 2001, 59, 407-414; Gabay and Kushner, N. Engl. J. Med., 1999, 340, 448-454; Highton et al., J. Rheumatol., 1985, 12, 871-875; Hulthe et al., Clin. Sci. (Colch), 2001, 100, 371-378; Lagrand et al., Circulation, 1999, 100, 96-102; Morrow and Ridker, Med. Clin. North. Am., 2000, 84, 149-161, ix; Szalai et al., Immunol. Res., 1997, 16, 127-136; Westhuyzen and Healy, Ann. Clin. Lab Sci., 2000, 30, 133-143; Yudkin et al., Atherosclerosis, 2000, 148, 209-214).
Improved methods of quantifying CRP have led to increased application to clinical medicine including diagnoses of urinary tract infections (Arici and Walls, Kidney Int., 2001, 59, 407-414), meningitis (Ruuskanen et al., J. Pediatr., 1985, 107, 97-100), neonatal sepsis, erythropoietin resistance (Barany, Nephrol. Dial. Transplant., 2001, 16, 224-227) and occult bacteremia, conditions in which CRP is usually elevated.
Structurally, CRP is a member of the pentraxin family of proteins, which are characterized by a cyclic pentameric structure and radial symmetry. The five identical 24-kDa protomers consist of 206 amino acids, and are noncovalently linked (Lei et al., J. Biol. Chem., 1985, 260, 13377-13383; Szalai et al., Immunol. Res., 1997, 16, 127-136). The genomic DNA sequence for human CRP has been reported by Lei et al. (Lei et al., J. Biol. Chem., 1985, 260, 13377-13383) as have mutant forms of the protein (Potempa et al., 1996) and methods to deliver materials into cells using the mutant protein as a carrier (Potempa et al., 2000). Polypeptides corresponding to amino acids 174-185 of CRP having immunomodulatory activity are disclosed and claimed U.S. Pat. No. 5,783,179 (Nestor et al., 1998). Peptides corresponding to positions 62-71 of human CRP have also been studied for their ability to inhibit the activity of human leukocyte elastase and/or cathepsin G for the treatment of inflammatory conditions and these are disclosed in the PCT Publication WO 99/00418 (Fridkin, 1999).
The CRP protein binds to a broad range of cellular substances such as phosphocholine, fibronectin, chromatin, histones, and ribonucleoprotein in a calcium-dependent manner (Szalai et al., Immuno. Res., 1997, 16, 127-136). It is a ligand for specific receptors on phagocytic leukocytes, mediates activation reactions on monocytes and macrophages, and activates complement (Szalai et al., Immunol. Res., 1997, 16, 127-136).
The function of CRP is felt to be related to its role in the innate immune system. Similar to Ig (Ig)G, it activates complement, binds to Fc receptors and acts as an opsonin for various pathogens. Interaction of CRP with Fc receptors leads to the generation of proinflammatory cytokines that enhance the inflammatory response. Unlike IgG, which specifically recognizes distinct antigenic epitopes, CRP recognizes altered self and foreign molecules based on pattern recognition. CRP is therefore thought to act as a surveillance molecule for altered self and certain pathogens. This recognition provides early defense and leads to a proinflammatory signal and activation of the humoral, adaptive immune system. Thus, the CRP molecule has both a recognition and an effector function.
The pharmacological modulation of C-reactive protein activity and/or expression is therefore believed to be an appropriate point of therapeutic intervention in pathological conditions.
Strategies aimed at modulating C-reactive protein function by targeting protein levels have involved the use of antibodies, peptides and molecules that inhibit HMG-CoA reductase.
Recently, Ridker et al. have demonstrated that lovastatin, an inhibitor of the enzyme HMG-CoA reductase, is an effective agent in reducing the risk of acute coronary events in participants with elevated CRP levels but no hyperlipidemia. In this trial, the use of lovastatin resulted in a 14.8 percent reduction in median CRP levels after one year whereas no change was observed in the placebo group (Ridker et al., N. Engl. J. Med., 2001, 344, 1959-1965). Another statin, cerivastatin, has also been demonstrated to lower CRP levels in patients with hypercholesterolemia (Ridker et al., Circulation, 2001, 103, 1191-1193).
However, there are currently no known therapeutic agents which effectively inhibit CRP levels and function. Consequently, there remains a long felt need for agents capable of effectively and selectively inhibiting CRP.
Antisense technology is emerging as an effective means for reducing the expression of specific gene products and may therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications for the modulation of CRP expression. The present invention provides compositions and methods for modulating CRP expression.